Hydrotreating process for residual oil

ABSTRACT

The invention relates to a method of heavy oil hydrogenation, precisely to a method of heavy oil hydrogenation for which a part of the catalyst to be used is a regenerated catalyst, and concretely to a method of heavy oil denitrification and to a method of heavy of desulfurization. It is characterized in that heavy oil is passed through a layer of a regenerated catalyst or a layer containing a regenerated catalyst. With the specific catalyst disposition employed in the method, heavy oil can be well hydrogenated under the same conditions as those for ordinary heavy oil hydrogenation with fresh catalysts. The method is significantly effective for efficient utilization of used catalysts.

TECHNICAL FIELD

The present invention relates to a method of hydrogenating heavy-oil.More precisely, it relates to a method of hydrogenating heavy oil with acatalyst partly comprising a regenerated catalyst, concretely, to amethod of denitrifying and desulfurizing heavy oil with such a catalyst.

BACKGROUND ART

For petroleum purification, there are many methods of purifyingdifferent fractions through hydrogenation. They include desulfurizationand denitrification of naphtha, kerosene, light oil, etc.;desulfurization, denitrification and cracking of heavy-gravity lightoil; and desulfurization and denitrification of residual oil and heavyoil. Of those, the catalysts used for hydrogenating naphtha, keroseneand light oil all having a relatively low boiling point and containingfew metal impurities such as vanadium and others are degraded only alittle.

The catalysts used for hydrogenating them will be degraded almostexclusively by a small amount of carbonaceous material depositedthereon. Therefore, the used catalysts could be regenerated and reusedif the carbonaceous deposit is removed from them, for example, by firingthe deposit. Removing the carbonaceous deposit to regenerate the usedcatalysts into reusable ones does not require any severe fire control,as the amount of the deposit is small. Even when once used, some usedcatalysts will be degraded only a little and could be directly reused asthey are. Therefore, the catalysts of that type could be used repeatedlyfor treating naphtha, kerosene, light oil and the like, not requiringany specific care.

Recently, hydrogenation catalysts for heavy-gravity light oil andreduced-pressure light oil have been reused through regeneration or thelike, and some methods for regenerating and reusing them have beenestablished. For example, it is known that, in the hydro-crackingprocess for heavy-gravity light oil, both the hydro-cracking catalystand the hydro-denitrification catalyst for the pretreatment can beregenerated and reused through hydrogen activation or oxygen activation.

On the catalysts used for hydrogenation of these petroleum distillates,few oil-derived metals such as vanadium and the like deposit, since thedistillates contain few metal impurities. In addition, the amount of thecarbonaceous material that may deposit on the used catalysts is smalland the carbonaceous deposit could be readily fired away. While thecatalysts with the carbonaceous deposit thereon are regenerated byfiring them, their surfaces will not be heated up to so hightemperatures, and the pore structure of the fired catalysts and even thecondition thereof to carry the active metal phase therein will changelittle. Therefore, the regenerated catalysts could be reused with nodifficulty for treating petroleum distillates such as heavy-gravitylight oil, reduced-pressure light oil and others (Studies in Surface andCatalysis, Vol. 88, p. 199, 1994).

However, in hydrogenation of residual oil having a higher boiling pointor of heavy oil containing undistillable fractions, a large amount ofmetallic material and carbonaceous material deposits on the usedcatalysts, since the oil to be processed contains a large amount ofmetal impurities and easily-carbonizing substances such as asphaltene,etc. In addition, from the viewpoint of their quality, the usedcatalysts having both the metallic deposit and the carbonaceous depositthereon could not be easily regenerated to remove the deposits therefromby firing them (Catal. Today, Vol. 17, No. 4, p. 539, 1993; Catal. Rev.Sci. Eng., 33 (3 & 4), p. 281, 1991). For these reasons, the usedcatalyst have heretofore been discarded without being recycled.

The present invention is to regenerate the catalysts used anddeactivated through hydrogenation of heavy oil and others, which haveheretofore been discarded without being recycled, and its object is toprovide a method of effectively using the regenerated catalysts forhydrogenation of heavy oil.

DISCLOSURE OF THE INVENTION

We, the present inventors have assiduously studied, and, as a result,have found that, when a catalyst having been deactivated throughhydrogenation of heavy oil and others is regenerated and when thecombination of the regenerated catalyst and a fresh catalyst isoptimized, then the combined catalyst system is still effective forhydrogenation of heavy oil. In addition, we have further found that,when the deactivated catalyst is regenerated in such a manner that theamount of the impurities still adhering to the regenerated catalyst andthe physical properties of the regenerated catalyst are controlled tofall within a specifically defined range, then the thus-regeneratedcatalyst is especially effective for hydrogenation of heavy oil. On thebasis of these findings, we have completed the present invention.

Specifically, the summary of the invention is as follows:

(1) A method of hydrogenating heavy oil, which is characterized bypassing heavy oil through at least a layer of a regenerated catalyst ora layer containing a regenerated catalyst.

(2) A method of hydro-denitrifying heavy oil in a reaction zone filledwith a catalyst, which is characterized by catalyst disposition of suchthat a regenerated catalyst is disposed in the former stage of at leasta part of the reaction zone and a fresh catalyst is disposed in thelatter stage thereof.

(3) The hydro-denitrifying method of above (2), wherein the amount ofthe fresh catalyst filled in at least a part of the reaction zone fallsbetween 20 and 95% by volume and that of the regenerated catalyst filledtherein falls between 5 and 80% by volume.

(4) A method of hydro-desulfurizing heavy oil in a reaction zone filledwith a catalyst, which is characterized by catalyst disposition of suchthat a fresh catalyst is disposed in the former stage of at least a partof the reaction zone and a regenerated catalyst is disposed in thelatter stage thereof.

(5) The hydro-desulfurizing method of above (4), wherein the amount ofthe regenerated catalyst filled in at least a part of the reaction zonefalls between 5 and 80% by volume and that of the fresh catalyst filledtherein falls between 20 and 95% by volume.

(6) A method of hydrogenating heavy oil, for which is used a reactionzone comprising at least three reaction layers of regenerated catalystlayers and fresh catalyst layers disposed alternately.

(7) The method of hydrogenating heavy oil of above (6), wherein theliquid hourly space velocity (LHSV) of the heavy oil passing through theregenerated catalyst layer to be hydrogenated therethrough is largerthan 1 hr⁻¹.

(8) A method of hydrogenating heavy oil, for which is used a reactionzone comprising a regenerated catalyst and a fresh catalyst and havingat least a mixed layer of the two.

(9) The method of hydrogenating heavy oil of any one of above (6) to(8), wherein the amount of the regenerated catalyst filled in thereaction zone falls between 5 and 80% by volume and that of the freshcatalyst filled therein falls between 20 and 95% by volume.

(10) The method of hydrogenating heavy oil of any one of above (1) to(9), wherein the vanadium content of the regenerated catalyst is at most35% by weight.

(11) The method of hydrogenating heavy oil of any one of above (1) to(10), wherein the carbon content of the regenerated catalyst is at most15% by weight.

(12) The method of hydrogenating heavy oil of any one of above (1) to(11), wherein the specific surface area of the regenerated catalystfalls between 60 and 200 m²/g.

(13) The method of hydrogenating heavy oil of any one of above (1) to(12), wherein the pore volume of the regenerated catalyst falls between0.3 and 1.0 cc/g.

(14) The method of hydrogenating heavy oil of any one of above (1) to(13), wherein the regenerated catalyst is from a used catalyst having atleast one metal of molybdenum, tungsten, cobalt and nickel carried on anoxide carrier, the catalyst having been used for hydrogenating mineraloil and then regenerated.

(15) The method of hydrogenating heavy oil of above (14), wherein theoxide carrier is alumina, and the metal carried on it is nickel andmolybdenum.

(16) The method of hydrogenating heavy oil of above (14), wherein theoxide carrier is alumina containing at least one oxide of phosphorus,boron or silicon, and the metal carried on it is nickel or cobalt, andmolybdenum.

(17) The method of hydrogenating heavy oil of any one of above (14) to(16), wherein the nickel or cobalt content of the catalyst having themetal carried on its carrier falls between 0.1 and 10% by weight and themolybdenum content thereof falls between 0.1 and 25% by weight.

(18) The method of hydrogenating heavy oil of any one of above (10) to(17), which is for hydro-denitrifying heavy oil.

(19) The method of hydrogenating heavy oil of any one of above (10) to(17), which is for hydro-desulfurizing heavy oil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view illustrating case 1 of the third aspect ofthe invention. In this, the rectangular outline indicates a reactor(reaction zone); and the upper and lower lines arrowed therearoundindicate the route of heavy oil being introduced into the reactor andthat of the processed product being taken out of it, respectively. Therectangles as specifically designated by (a) and (b) in the reactorindicate different catalyst layers. (The same shall apply to the otherdrawings referred to herein.)

FIG. 2 is a conceptual view illustrating case 2 of the third aspect ofthe invention.

FIG. 3 is a conceptual view illustrating case 3 of the third aspect ofthe invention. In this, the reactor is seen to be composed of sixcatalyst layers. However, this shall conceptually show at least 4catalyst layers of (a) and (b) as alternately and repeatedly disposed inthe illustrated order.

FIG. 4 is a conceptual view illustrating case 4 of the third aspect ofthe invention. (The same as in FIG. 3 shall apply to this.)

FIG. 5 is a conceptual view illustrating case 5 of the third aspect ofthe invention. In this, the rectangles indicate different reactors, andthe lines arrowed therearound indicate the route of heavy oil beingintroduced into and having passed through the reactors and that of theprocessed product being taken out of them, respectively. The threereactors constitute one reaction zone. (The same shall applyhereinunder.)

FIG. 6 is a conceptual view illustrating case 6 of the third aspect ofthe invention.

FIG. 7 is a conceptual view illustrating case 7 of the third aspect ofthe invention.

FIG. 8 is a conceptual view illustrating case 8 of the third aspect ofthe invention.

FIG. 9 is a conceptual view illustrating case 9 of the third aspect ofthe invention.

FIG. 10 is a conceptual view illustrating case 10 of the third aspect ofthe invention.

FIG. 11 is a conceptual view illustrating case 11 of the third aspect ofthe invention.

FIG. 12 is a conceptual view illustrating case 12 of the third aspect ofthe invention.

In these drawings, the reference code (a) indicates a fresh catalystlayer; (b) indicates a regenerated catalyst layer; and (c) indicates amixed catalyst layer.

BEST MODES OF CARRYING OUT THE INVENTION

Modes of carrying out the invention are described below.

1. Characteristic features of the invention:

In the invention of hydrogenating heavy oil, heavy oil must be passedthrough at least a layer of a regenerated catalyst or a layer containinga regenerated catalyst. Specifically, the invention is characterized inthat heavy oil to be processed is passed through a layer filled withonly a regenerated catalyst or through a layer containing a regeneratedcatalyst, or that is, a layer of a mixed catalyst of a regeneratedcatalyst and a fresh catalyst, but not through only a catalyst layerfilled with only a fresh catalyst, as will be described in detailhereinunder. The order of the fresh catalyst-filled layer and theregenerated catalyst-filled layer through which heavy oil is firstpassed is not specifically defined, but may be suitably selected fromvarious embodiments to be mentioned hereinunder, depending on the objectof the invention.

Various embodiments of the invention all satisfying the intended objectare described below.

(1) Method of hydro-denitrification (first aspect of the invention):

The first aspect of the invention is a method of hydro-denitrifyingheavy oil in a reaction zone filled with a catalyst, which ischaracterized by using a specific combination of a regenerated catalystand a fresh catalyst. Specifically, the hydro-denitrifying method ischaracterized by specific catalyst disposition of such that aregenerated catalyst is disposed in the former stage of at least a partof the reaction zone and a fresh catalyst is disposed in the latterstage thereof.

Heavy oil is processed for various purposes through hydrogenation. Theessential object of the process of heavy oil hydrogenation is fordesulfurization and cracking of heavy oil. In many cases, however, theprocess is also for reducing the nitrogen content of the processed oil.For example, in the process of desulfurization for heavy oil production,the sulfur content and also the nitrogen content and the metal contentof the product heavy oil are important quality control items in manycases. The process of desulfurization of heavy oil is often employed forpretreatment for the catalytic cracking process for gasoline production.The crude oil to be catalytically cracked for that purpose is requiredto have a reduced sulfur content and even a reduced nitrogen content asthe important factors of itself. On the other hand, in thehydro-cracking process of crude oil, the nitrogen compound which may bein the crude oil and which will act as a catalyst poison to the crackingcatalyst will have to be previously removed from the crude oil throughpre-denitrification.

The denitrification in the process of hydrogenating heavy oil is meantto indicate various types of denitrification such as those mentionedabove, naturally including the denitrification to be effected for theessential object of itself but even any other types of denitrificationto be effected along with other reactions or to be effected aspre-treatment or post-treatment for other reactions. In thehydro-cracking process in which the denitrification is effected for thepre-treatment of the cracking catalyst to be used, the pre-treatmentshall correspond to the denitrification discussed herein.

The catalyst to be filled in the reaction zone as referred to hereinincludes not only the catalyst for only denitrification but also anyother catalysts essentially for desulfurization, de-scaling or metalremoval so far as they have the activity of denitrification and actuallyact for denitrification in the reaction zone. Accordingly, the reactionzone in the process of desulfurization and also denitrification of heavyoil will be meant to indicate not only an ordinary denitrificationreaction zone in the narrow sense of the word but also the entirereaction zone for the desulfurization process with various catalystlayers that covers a desulfurization zone, a metal-removing zone, ade-scaling zone, etc. At least a part of the reaction zone in that senseshall indicate not only the narrow-sense denitrification zone,desulfurization zone, metal-removing zone, de-scaling zone or the likebut also a part of the individual reactors in the entire reaction zoneand a part of the individual catalyst beds in each reactor. That part ofthe reaction zone may cover an area that bridges a downstream area ofone reactor and the upstream area of the next reactor. Accordingly, thewording “at least a part of the reaction zone” as referred to hereinshall indicate any and every one integrated part in which heavy oil isdenitrified even in some degree irrespective of the object essential toor subsidiary to the invention.

Typical embodiments of a part the reaction zone include one entiredenitrification zone, a combination of plural reactors connected inseries, one reactor, one catalyst bed only in a reactor, etc. As thecase may be, the reaction zone for denitrification with metal removaland the reaction zone for denitrification with desulfurization may beconsidered as different zones. In that case, each of the two reactionzones may be divided into a former stage and a latter stage in which thecatalyst is disposed as specifically defined herein. However, thewording “at least a part of the reaction zone” as referred to herein forspecific catalyst disposition shall not include catalyst zones notparticipating at all in denitrification. For example, the catalyst zonefor only hydro-cracking is outside the scope of the denitrificationzone.

Regarding the catalyst disposition in the invention, it is importantthat a regenerated catalyst is in the former stage of at least a part ofthe reaction zone and a fresh catalyst is in the latter stage thereof.This is because the specific catalyst disposition enables effectivedenitrification of heavy oil in such a preferred manner that theeasily-removable nitrogen compound existing in heavy oil is firstremoved through denitrification with the regenerated catalyst andthereafter the other nitrogen compound which still remains in thethus-processed heavy oil and which is poorly reactive is removed throughdenitrification with the fresh catalyst having a relatively highactivity. For this, a regenerated catalyst having a relatively lowerhydrogenation activity shall be disposed in the former stage and a freshcatalyst having a relatively higher hydrogenation activity in the latterstage to attain better results.

In order that a part of the reaction zone (this will be hereinafterreferred to as “specific reaction zone”) could satisfactorily attain theintended object in the hydro-denitrification process, it is desirablethat the fresh catalyst accounts for at least 20% of the specific zone(this indicates % by volume of the total catalyst in the specificreaction zone filled with the catalyst, and the same shall applyhereinunder), more preferably at least 40% thereof. On the contrary,however, it is desirable that the amount of the regenerated catalyst inthe specific zone is at least 5%, more preferably at least 10%. If not,the improvement in the denitrification by the specific catalystdisposition in the invention will not be significant.

The former stage and the latter stage for the catalyst disposition asreferred to herein indicate the upstream area of the reaction flow andthe downstream area thereof, respectively. Accordingly, the catalystdisposed in a relatively upstream area shall be one in the former stage,and that disposed in a relatively downstream area shall be in the latterstage.

(2) Method of hydro-desulfurization (second aspect of the invention):

The second aspect of the invention is a method of hydro-desulfurizingheavy oil in a reaction zone filled with a catalyst, which ischaracterized by using a specific combination of a regenerated catalystand a fresh catalyst. Specifically, the hydro-desulfurizing method ischaracterized by specific catalyst disposition of such that a freshcatalyst is disposed in the former stage of at least a part of thereaction zone and a regenerated catalyst is disposed in the latter stagethereof. The catalyst to be filled in the reaction zone includes notonly the catalyst for only desulfurization but also any other catalystsessentially for de-scaling or metal removal. Accordingly, the reactionzone will be meant to indicate not only an ordinary desulfurizationreaction zone in the narrow sense of the word but also the entirereaction zone for the desulfurization process with various catalystlayers that covers a metal-removing zone, a de-scaling zone, etc.

At least a part of the reaction zone in that sense may be the entirereaction zone, but including any of the narrow-sense desulfurizationzone, metal-removing zone, de-scaling zone or the like, as well as apart of those reaction zones and also a combination of a plurality ofsuch reaction zones. It further includes one reactor and even onecatalyst bed part in a reactor. As the case may be, it may cover an areathat bridges a downstream area of one reactor and the upstream area ofthe next reactor. Accordingly, the wording “at least a part of thereaction zone” as referred to herein shall indicate any and every oneintegrated part in which heavy oil is desulfurized even in some degreeirrespective of the object essential to or subsidiary to the invention.

Typical embodiments of a part the reaction zone include a metal-removingzone only, a narrow-sense desulfurization zone except metal-removing andde-scaling zones, one or plural reactors in the desulfurization zone,and one or plural catalyst beds in a reactor.

Regarding the catalyst disposition in the invention, it is importantthat a fresh catalyst is in the former stage of at least a part of thereaction zone and a regenerated catalyst is in the latter stage thereof.This is because desulfurization of heavy oil is greatly interfered withthe aromatic component of the starting heavy oil. Therefore, it isbelieved that a method of first hydrogenating as much as possible thestarting heavy oil and thereafter further hydrogenating the resultinghydrogenate intermediate to give desulfurized oil and hydrogen sulfidewill be effective desulfurization of heavy oil. For this, a freshcatalyst having a relatively higher hydrogenation activity shall bedisposed in the former stage and a regenerated catalyst having asomewhat lower hydrogenation activity in the latter stage to attainbetter results.

In order that a part of the reaction zone (this will be hereinafterreferred to as “specific reaction zone”) could satisfactorily attain theintended object in the hydro-desulfurization process, it is desirablethat the fresh catalyst accounts for at least 20% of the specific zone(this indicates % by volume of the total catalyst in the specificreaction zone filled with the catalyst, and the same shall applyhereinunder), more preferably at least 40% thereof. On the contrary,however, it is desirable that the amount of the regenerated catalyst inthe specific zone is at least 5%, preferably at least 10%. If not, theimprovement in the desulfurization by the specific catalyst dispositionin the invention will not be significant.

The former stage and the latter stage for the catalyst disposition asreferred to herein indicate the upstream area of the reaction flow andthe downstream area thereof, respectively. Accordingly, the catalystdisposed in a relatively upstream area shall be one in the former stage,and that disposed in a relatively downstream area shall be in the latterstage.

(3) Method of hydrogenation (third aspect of the invention):

The third aspect of the invention is a method of hydrogenating heavy oilin a reaction zone filled with a catalyst, which is characterized byspecific disposition of a regenerated catalyst and a fresh catalyst inthe reaction zone. Heavy oil processing is seldom directed to onlyeither one of desulfurization or denitrification, but is often directedto both the two in a well balanced manner. Therefore, it is effectivefor that purpose to combine the first and second aspects of theinvention.

One embodiment of the combination is hydrogenation of heavy oil in areaction zone filled with a catalyst, in which the catalyst is dodisposed that regenerated catalyst layers and fresh catalyst layers aredisposed alternately in at least three layers.

The most basic cases of the embodiment is case 1 illustrated in FIG. 1and case 2 in FIG. 2. The catalyst disposition of case 1 is the mostpopular one for hydro-desulfurization of heavy oil, for which a freshcatalyst layer (for hydro-desulfurization of heavy oil, this preferablycomprises a catalyst for metal removal and a catalyst fordesulfurization), a regenerated catalyst layer (forhydro-desulfurization of heavy oil, this is preferably a desulfurizationcatalyst layer), and a fresh catalyst layer (for hydro-desulfurizationof heavy oil, this is preferably a desulfurization catalyst layer) aredisposed in that order from the upstream side of the oil flow.

The catalyst disposition of case 2 is opposite to that of case 1, forwhich a regenerated catalyst layer, a fresh catalyst layer and aregenerated catalyst layer are disposed in that order from the upstreamof the oil flow. Case 2 is suitable to hydro-cracking of heavy oil.Specifically, in case 2, a regenerated catalyst still having goodcapability for metal removal may be in the first regenerated catalystlayer; a fresh hydro-cracking catalyst may be in the next fresh catalystlayer; and a regenerated catalyst for post-desulfurization may be in thelast regenerated catalyst layer.

The basic catalyst disposition in the invention is as above. Forattaining satisfactory hydrogenation of heavy oil in those cases, theliquid hourly space velocity (LHSV) of the heavy oil passing through thecatalyst layers is desirably as small as possible so that the heavy oilcould have plenty of residence time in the layers. However, if the heavyoil being processed has too much residence time in the regeneratedcatalyst layer, it will unfavorably pyrolyze or give carbonaceousproducts therein. To evade such unfavorable side reactions, it will bedesirable that, after the heavy oil has been kept for a predeterminedperiod of residence time in one regenerated catalyst layer, it istransferred into the next fresh catalyst layer having high capabilityfor hydrogenation so that it can undergo hydrogenation therein to asatisfactory degree without being accompanied by unfavorable sidereactions of pyrolysis or carbonization to give unfavorable carbonaceousside products. For this, it will be desirable that the regeneratedcatalyst layers and the fresh catalyst layers are combined and disposedin at least three layers and that the heavy oil that passes through thelayers could have LHSV through each one regenerated layer of at least 1hr⁻¹, more preferably at least 1.5 hrs⁻¹.

Case 3 illustrated in FIG. 3 and case 4 in FIG. 4 are preferred cases ofthe catalyst disposition as above. In addition, these are for the methodof using a plurality of regenerated catalysts having different functionsin which the plural regenerated catalysts are disposed in plural layers.

In many practical devices for hydrogenation of heavy oil, for example,for hydro-desulfurization thereof, at least 2 reactors are connected asin case 5 of FIG. 5 or case 6 of FIG. 6. (In the cases of FIG. 5 andFIG. 6, three reactors are connected.) In those cases, each reactor maybe filled with a fresh catalyst or a regenerated catalyst to have afresh catalyst layer or a regenerated catalyst layer therein; or onereactor may have both a fresh catalyst layer and a regenerated catalystlayer. In particular, the catalyst layer disposition for heavy oilhydro-desulfurization as in case 6 is preferred, as it could producebetter hydrogenation results.

In another embodiment of heavy oil hydrogenation of the invention, aregenerated catalyst and a fresh catalyst are so disposed that the twoare mixed in one mixed layer.

Case 7 of FIG. 7 is the basic catalyst disposition of this embodiment,in which the mixed layer is filled in one reactor. Case 8 of FIG. 8 andcase 9 of FIG. 9 are modifications of the basic catalyst disposition.FIG. 10 (case 10) illustrates a modification of case 1 and case 7. Thiscomprises reactors (a) and (c). In this, however, the reactor (a) may bereplaced with a reactor (b). For a plurality of reactors to beconnected, employable are embodiments of FIG. 11 and FIG. 12. In theembodiment of FIG. 12, the ratio of the regenerated catalyst to thefresh catalyst may vary in different mixed layers. In addition, theregenerated catalyst and the fresh catalyst may be so combined that theratio of the two differs in one mixed layer. Needless-to-say, pluralreactors may be so connected that some of them are of a catalyst layerof a regenerated catalyst alone.

Heavy oil is processed for various purposes through hydrogenation. Theessential object of the process of heavy oil hydrogenation is fordesulfurization and cracking of heavy oil. In many cases, however, theprocess is also for reducing the metal content and the nitrogen contentof the processed oil. For example, in the process of desulfurization forheavy oil production, the sulfur content and also the nitrogen contentand the metal content of the product heavy oil are important qualitycontrol items in many cases. The process of desulfurization of heavy oilis often employed for pretreatment for the catalytic cracking processfor gasoline production. The crude oil to be catalytically cracked forthat purpose is required to have a reduced sulfur content and even areduced metal content, a reduced nitrogen content and a reduced heavyaromatic content as the important factors of itself. On the other hand,in the hydro-cracking process of crude oil, the nitrogen compound whichmay be in the crude oil and which will act as a catalyst poison to thecracking catalyst will have to be previously removed from the crude oilthrough pre-denitrification.

Heavy oil hydrogenation as referred to herein is meant to indicatevarious types of hydrogenation of heavy oil such as those mentionedabove, naturally including desulfurization, metal removal treatment,denitrification, cracking and others for processing heavy oil.Needless-to-say, combinations of one reaction for dehydrogenation withany others, and also the pre-treatment and the post-treatment to beeffected before or after the main reaction for hydrogenation shall bewithin the scope of the terminology, heavy oil hydrogenation referred toherein.

The catalyst to be filled in the reaction zone as referred to hereinincludes not only the catalyst for only one limited function but alsoany other catalysts essentially for desulfurization, de-scaling or metalremoval, further including even others for denitrification as combinedwith the essential function.

The third aspect of the invention is preferable to using a reaction zonethat comprises a regenerated catalyst and a fresh catalyst merelycombined in series therein, as leading to favorablehydro-desulfurization of heavy oil, favorable hydro-denitrificationthereof and even favorable hydrogenation thereof for metal removal.Concretely, one problem with heavy oil hydrogenation through a reactionzone where a fresh catalyst layer is disposed in the former stage and aregenerated catalyst layer is in the latter stage is that the heavy oilbeing processed could be favorably desulfurized with metals being alsofavorably removed from it, but its denitrification is difficult. On theother hand, heavy oil hydrogenation through a reaction zone where aregenerated catalyst layer is disposed in the former stage and a freshcatalyst is in the latter stage is also problematic in that the heavyoil being processed could be favorably denitrified but is hardlydesulfurized and, in addition, metal removal from it is difficult. Thecatalyst disposition in the third aspect of the invention solves theproblems with the two cases, and leads to more efficient heavy oilhydrogenation, taking the advantages of the two cases. For betterresults in the heavy oil hydrogenation of this aspect, using too muchregenerated catalyst is unfavorable. In this aspect, it is desirablethat the fresh catalyst to be used accounts for at least 20% of theentire catalyst zone (this indicates % by volume of the total catalystin the entire reaction zone filled with the catalyst, and the same shallapply hereinunder), more preferably at least 40% thereof. On thecontrary, however, it is desirable that the amount of the regeneratedcatalyst in the entire catalyst zone is at least 5%, more preferably atleast 10%. If not, the improvement in the heavy oil hydrogenation by thespecific catalyst disposition in this aspect of the invention will notbe significant.

2. Details of the invention (first to third aspects mentioned above):

(1) Heavy oil as referred to herein includes petroleum distillationresidues such as normal-pressure residual oil, reduced-pressure residualoil and the like residual fractions, but does not include fractions ofdistillate oil only, such as kerosene, light oil, reduced-pressure lightoil, etc. In general, heavy oil has a sulfur content of 1% by weight ormore, a nitrogen content of 200 ppm by weight or more, a residualcarbonaceous content of 5% by weight or more, a vanadium content of 5ppm or more, and an asphaltene content of 0.5% or more. For example, itincludes, in addition to the normal-pressure residual oil and otherresidual fractions noted above, crude oil, asphalt oil,thermally-cracked oil, tar-sand oil, and even mixed oil comprising them.For the heavy oil hydrogenation of the invention, used are fixed-bedreactors. The process of the invention is not directed to any othermoving-bed reactors, boiling-bed reactors, etc. The oil flow through thereaction may be either in the up-flowing direction or in thedown-flowing direction.

(2) The fresh catalyst, the regenerated catalyst, and the regenerationof catalysts are described. The fresh catalyst for use in the inventionis one as prepared for hydrogenation of mineral oil, preferably fordesulfurization, metal removal, denitrification, cracking and the likeof mineral oil, or may be of any others additionally having thecapabilities of hydrogenation that includes desulfurization, metalremoval, denitrification, cracking and the like of mineral oil. As thefresh catalyst to that effect, for example, usable are ordinary,commercially-available hydro-desulfurization catalysts, hydrogenatingand metal-removing catalysts, etc. As the case may be, specificcatalysts having the function of oil hydrogenation may be prepared foruse herein. The fresh catalyst includes not only those not used anywherefor oil hydrogenation but also those having been once used for oilhydrogenation with using them being stopped within a short period oftime owing to machine trouble or the like, and therefore capable ofbeing again used directly as they are. For the latter, even thecatalysts having been once used only within a short period of time arewithin the scope of the fresh catalyst, so far as they still have theoriginal hydrogenation activity without being specifically processed forre-activation.

The regenerated catalyst as referred to herein is one as obtained byregenerating a used catalyst. Specifically, a fresh catalyst such asthat noted above is once used for hydrogenation of heavy oil or the liketo such a degree that the used catalyst could no more have asatisfactory degree of hydrogenation activity (this is hereinafterreferred to as used catalyst), and the used catalyst in that conditionis re-activated through regeneration treatment into the regeneratedcatalyst for use herein. The dehydrogenation which the fresh catalystundergoes is generally desulfurization, but may include any others of,for example, metal removal, denitrification, removal of aromaticresidues, and cracking. In general, catalysts used for processing heavyoil are regenerated into the regenerated catalysts for use herein.However, catalysts used for hydrogenating distillate oil fractions suchas heavy-gravity light oil and others may be regenerated into theregenerated catalysts for use herein. Anyhow, the regenerated catalystreferred to herein encompasses all types of used and regeneratedcatalysts that can be again used for heavy oil hydrogenation.

To regenerate them, for example, used catalysts may be washed withsolvents to remove oily residues from them; they are fired to removecarbonaceous residues, sulfur residues, nitrogen residues and othersfrom them; or they are screened to remove the aggregated blocks or thepulverized fine grains from them and to select normally-shaped grainsfrom them. Preferably, in the invention, used catalysts are oxidized toremove carbonaceous residues from them, thereby obtaining the intendedregenerated catalysts usable herein. More preferably, used catalysts aretaken out of reactors and oxidized outside the reactors to removecarbonaceous residues from them. In the regeneration treatment, it isnot always necessary to completely remove all carbonaceous residues fromthe used catalysts.

One preferred embodiment of regenerating used catalysts is described.The used catalyst to be regenerated is first washed with a solvent. Asthe solvent, preferably used are toluene, acetone, alcohol, andpetroleum fractions such as naphtha, kerosene, light oil, etc. Any othersolvents are usable, so far as they can easily dissolve the organicsubstances having adhered to the used catalysts. To wash the usedcatalyst, light oil may be circulated through the hydrogenation reactorin which the catalyst is still therein, and thereafter nitrogen gas orthe like may be passed through it at a temperature falling between 50and 200° C. or so thereby drying the catalyst. In another embodiment,the catalyst having been first washed with the circulating light oil istaken out of the reactor, and is kept wetted with the light oil toprevent it from becoming too hot or from being spontaneously fired, andthereafter it may be dried in any desired time. In still anotherembodiment, the used catalyst taken out of the reactor may be ground topulverize the aggregates; or the powdery fragments and also scale andother impurities may be removed from it. In this, the thus-processed,used catalyst is washed with light oil and then with naphtha, and isthereafter dried. The mechanical pre-treatment facilitates the step ofwashing and drying the used catalyst. Toluene is favorable to washing asmall amount of the used catalyst, as completely removing oily residuesfrom it.

The catalyst having been thus washed to remove oily residues andimpurities from it must be oxidized to remove carbonaceous residues, inorder that the catalyst could exhibit its activity to a satisfactorydegree. To oxidize it, in general, the catalyst is fired in an oxidizingatmosphere having a controlled temperature and a controlled oxygenconcentration. If the temperature of the atmosphere is too high, or ifthe oxygen content thereof is too large, the surface of the catalystwill be heated too much so that the crystal morphology of the metalcarried therein and even the metal-carrying condition of the catalystwill vary, or the pores existing in the carrier of the catalyst willreduce and the activity of the catalyst will be lowered. On thecontrary, if the temperature of the atmosphere is too low, or if theoxygen content thereof is too small, the carbonaceous residues existingin the catalyst could not be sufficiently fired and removed away, andregenerating the catalyst to make it have a satisfactory degree ofactivity will be impossible. Preferably, the atmosphere temperaturefalls between 200 and 800° C., more preferably between 300 and 600° C.

It is desirable that the oxygen content of the oxidizing atmosphere iscontrolled to fall between 1 and 21%. However, depending on the firingmethod, especially on the condition how the catalyst is contacted withthe firing gas, the oxygen content of the atmosphere may be controlledto fall within a desired range. It is important to oxidize and removethe carbonaceous residues from the catalyst while controlling thesurface temperature of the catalyst by varying the temperature and theoxygen content of the atmosphere and varying the flow rate of theatmosphere gas. It is also important to prevent the regenerated catalystfrom having a reduced specific surface area and a reduced pore volume,while preventing the crystal structure of the hydrogenation-activemetal, nickel or molybdenum, in the catalyst from being varied throughthe oxidation treatment, and further preventing the condition of thecrystal grains carried in the catalyst from being varied therethrough.

It is desirable that the fired catalyst is screened through sieving orthe like to remove powdery fine grains and others, thereby selectingonly the normally-shaped grains from it for use here in as theregenerated catalyst. If not screened, the catalyst layer will beclogged with the oil flow running therethrough or the oil flow will beundesirably channeled through the catalyst layer, whereby the flowpressure loss in the reactor will increase and it would becomeimpossible to smoothly drive the reaction system, even though theinitial activity of the regenerated catalyst could be high to asatisfactory degree.

(3) The composition and the physical properties of the regeneratedcatalyst are described.

The vanadium content and the carbonaceous substance content of catalystshaving been used for hydrogenation are the factors indicating the degreeof degradation of the used catalysts. In general, vanadium is not incatalysts for hydrogenation, but is derived from minor impurities incrude oil to be hydrogenated. Therefore, the vanadium content of usedcatalysts could be one factor indicating the degree of degradation ofthe used catalysts. Of the regenerated catalyst for use herein, thevanadium content is preferably at most 35%, more preferably at most 20%,even more preferably from 3 to 15%. (In this connection, the metalcontent of the catalyst referred to herein is based on the weight of thecatalyst having been oxidized at a temperature not lower than 400° C.until it shows no more weight loss, and is represented in terms of % byweight of the metal in the form of its oxide. The same shall apply tothe content of other metals in catalysts.) If the vanadium content ofthe regenerated catalyst is larger than 35%, the activity thereof willbe too low. If such a low-activity regenerated catalyst is used herein,hydrogenation could not be attained to a satisfactory degree. On theother hand, if its vanadium content is smaller than 2%, the regeneratedcatalyst still has its satisfactorily high activity. Even though such ahigh-activity regenerated catalyst is specifically disposed as in theinvention, the difference between the specific catalyst disposition andany other ordinary catalyst disposition for hydrogenation will be small.Therefore, in the invention, the vanadium content of the regeneratedcatalyst to be used preferably falls between 2 and 35%, more preferablybetween 3 and 15%. With the vanadium content falling within thepreferred range, the specific catalyst disposition of the regeneratedcatalyst produces better results.

For elementary analysis for vanadium and others, the sample to beanalyzed is fired at 650° C. for 1 hour. For Mo, P and V, the resultingash is dissolved in an acid and the resulting solution is analyzedthrough inductively-coupled plasma emission absorptiometry; and for Co,Ni and Al, the ash is mixed with lithium tetraborate, the resultingmixture is formed into glass beads under high-frequency heat, and theglass beads are analyzed through fluorescent X-ray spectrometry.

Also preferably, the carbon content of the regenerated catalyst for usein the invention is at most 15%, more preferably at most 10%. (Thecarbon content of the catalyst referred to herein is based on the weightof the catalyst having been oxidized at a temperature not lower than400° C. until it shows no more weight loss, and is represented in termsof % by weight of carbon in the catalyst. The same shall applyhereinunder.) Most used catalysts have a carbon content of from 10 to70% or so, and their carbon content can be reduced through regenerationtreatment to remove the carbonaceous substances from them. The activityof used catalysts having a large carbon content is low, as theirsurfaces are covered with carbonaceous substances. Reducing the carboncontent of such used catalysts through regeneration treatment recoverstheir activity. The carbon content and the sulfur content of catalystsare measured with a C and S co-analyzer.

(4) The catalyst regeneration treatment is accompanied by oxidation ofcatalysts, generally by firing of catalysts. During the treatment,therefore, the catalyst surface is often overheated whereby the porestructures of the treated catalysts will be changed and the condition ofthe metal carried in the catalysts will be also changed. As a result,the catalyst activity will be often lowered. The specific surface areaand the pore volume of regenerated catalysts may be the factorsindicating their catalytic activity, and based on these, the activity ofregenerated catalysts can be evaluated. The specific surface area andthe pore volume of catalysts gradually decrease while the catalysts areused for hydrogenation, since some impurities adhere to the usedcatalysts and since the catalysts are degraded under heat during thereaction. For the regenerated catalysts usable in the invention, it isdesirable that their specific surface area and pore volume are bothstill at least 70% of the initial values of the fresh catalysts. For theconcrete physical data of the regenerated catalysts, it is desirablethat their specific surface area falls between 60 and 200 m²/g, morepreferably between 10 and 200 m²/g, and their pore volume falls between0.3 and 1.0 cc/g. These data are obtained through nitrogen absorption.

(5) The regenerated catalysts are used for hydrogenation of heavy oil.Naturally, therefore, they must have the capability of hydrogenation. Astheir basic constitution, preferred are catalyst compositions comprisinga metal oxide with molybdenum, tungsten, cobalt or nickel carried on anoxide carrier of, for example, alumina, alumina-phosphorus,alumina-boron, alumina-silicon or the like. (In the carrier, phosphorus,boron and silicon are in the form of their oxide, and the same shallapply hereinunder.) Of those, more preferred are catalysts ofnickel/molybdenum carried on an alumina carrier; catalysts ofnickel/molybdenum carried on an alumina-phosphorus carrier; catalysts ofcobalt/molybdenum carried on an alumina-born carrier; and catalysts ofnickel/molybdenum carried on an alumina-silicon carrier. In addition,since the catalysts are for processing heavy oil, it is also desirablethat they contain the carried metals, cobalt or nickel, and molybdenum,in an amount of from 0.1 to 10% for cobalt or nickel and in an amount offrom 0.2 to 25% for molybdenum. On the other hand, the phosphoruscontent of the catalysts preferably falls between 0.1 and 15%. (This ismeasured in the same manner as that for the metal content measurementnoted above.)

3. Concrete reaction conditions for the first to third aspects of theinvention:

(1) The first aspect of the invention for heavy oilhydro-desulfurization including hydro-denitrification is describedconcretely. The reaction conditions for this are not specificallydefined, so far as the specific catalyst disposition is employed in thisaspect. General conditions for this aspect are described. Regarding thecatalyst disposition, it is desirable that a fresh catalyst for metalremoval is disposed in the metal removal zone, and a fresh catalyst fordesulfurization and denitrification is in the former half stage, 50%, ofthe desulfurization and denitrification zone while a regeneratedcatalyst for desulfurization and denitrification is in the latter halfstage, 50%, thereof. The heavy oil to be processed herein may be any onementioned above, but is preferably normal-pressure residual oil.Regarding the reaction conditions for it, the temperature may fallgenerally between 300 and 450° C., but preferably between 350 and 420°C.; the hydrogen partial pressure may fall generally between 7.0 and25.0 Pa, but preferably between 10.0 and 15.0 Pa; the liquid hourlyspace velocity may fall generally between 0.01 and 10 hrs⁻¹, butpreferably between 0.1 and 5 hrs⁻¹; and the ratio of hydrogen/oil mayfall generally between 500 and 2500 Nm³/kl, but preferably between 500and 2000 Nm³/kl.

To control the nitrogen content, the sulfur content and the metalcontent (nickel, vanadium) of the processed oil, the necessary factorsof the reaction conditions noted above, for example, the reactiontemperature may be suitably varied. According to the heavy oilhydro-denitrification of the invention as above, used catalysts whichhave heretofore been considered useless can be effectively recycled fordenitrification of residual oil, etc.

(2) The second aspect of the invention for heavy oilhydro-desulfurization, which is characterized by the specific catalystdisposition as above, is described concretely. The reaction conditionsfor this are not specifically defined, so far as the specific catalystdisposition is employed in this aspect. General conditions for thisaspect are described. The heavy oil to be processed herein may be anyone mentioned above, but is preferably normal-pressure residual oil.Regarding the reaction conditions for it, the temperature may fallgenerally between 300 and 450° C., but preferably between 350 and 420°C.; the hydrogen partial pressure may fall generally between 7.0 and25.0 Pa, but preferably between 10.0 and 15.0 Pa; the liquid hourlyspace velocity may fall generally between 0.01 and 10 hrs⁻¹, butpreferably between 0.1 and 5 hrs⁻¹; and the ratio of hydrogen/oil mayfall generally between 500 and 2500 Nm³/kl, but preferably between 500and 2000 Nm³/kl.

To control the sulfur content and the metal content (nickel, vanadium)of the processed oil, the necessary factors of the reaction conditionsnoted above, for example, the reaction temperature may be suitablyvaried. According to the heavy oil hydro-desulfurization of theinvention as above, used catalysts which have heretofore been considereduseless can be effectively recycled for desulfurization of residual oil,etc.

(3) The third aspect of the invention for heavy oil hydrogenation isdescribed concretely with reference to hydro-desulfurization of heavyoil. The reaction conditions for this are not specifically defined, sofar as the specific catalyst disposition as combined with the specificmode of filling catalysts in the reaction zone is employed in thisaspect. General conditions for this aspect are described. For thecatalyst disposition, any and every mode mentioned above is employable.The embodiment of case 6 of FIG. 6 is referred to herein. In thisembodiment, it is desirable that a fresh catalyst layer forhydrogenation and metal removal is disposed in the metal removal zone,which accounts for 10% of the total of all catalyst layers; a freshcatalyst layer for hydro-desulfurization is in 40% thereof in the formerstage of the desulfurization zone; are generated catalyst layer forhydro-desulfurization is in the next 20% thereof; and a fresh catalystlayer for hydro-desulfurization is in the final 30% thereof.

The heavy oil to be processed herein may be any one mentioned above, butis preferably normal-pressure residual oil. Regarding the reactionconditions for it, the temperature may fall generally between 300 and450° C., but preferably between 350 and420° C.; the hydrogen partialpressure may fall generally between 7.0 and 25.0 Pa, but preferablybetween 10.0 and 15.0 Pa; the liquid hourly space velocity may fallgenerally between 0.01 and 10 hrs⁻¹, but preferably between 0.1 and 5hrs⁻¹; and the ratio of hydrogen/oil may fall generally between 500 and2500 Nm³/kl, but preferably between 500 and 2000 Nm³/kl. In the case ofthe catalyst disposition mentioned above, the liquid hourly spacevelocity through the regenerated catalyst layer is preferably at least1.0 hr⁻¹.

To control the sulfur content, the nitrogen content and the metalcontent (nickel, vanadium) of the processed oil, the necessary factorsof the reaction conditions noted above, for example, the reactiontemperature may be suitably varied. According to the heavy oilhydrogenation of the invention as above, used catalysts which haveheretofore been considered useless can be effectively recycled forhydrogenation of residual oil, etc.

EXAMPLES

The invention is described concretely with reference to the followingExamples, which, however, are not intended to restrict the scope of theinvention.

Example 1 (first aspect of the invention)

A commercially-available catalyst carrying nickel and molybdenum on analumina carrier (this is referred to as fresh catalyst 1) was filled ina residual oil hydro-desulfurization device, into which was appliednormal-pressure residual oil from the Middle East, for 8000 hours.Hydro-desulfurizing the residual oil was continued while the reactiontemperature was so monitored that the sulfur content of the essentialfraction (distillate having a boiling point of not lower than 343° C.)of the processed oil could be stabilized on a constant level. This is toprepare a used catalyst from the fresh catalyst. Typical properties ofthe normal-pressure residual oil processed herein are given in Table 1;and the reaction conditions for desulfurization are in Table 2.

The used catalyst was taken out of the reactor, well washed withtoluene, and then dried (this is referred to as washed catalyst 1). Thewashed catalyst was oxidized in air at 500° C. for 3 hours (theresulting catalyst is referred to as regenerated catalyst 1). Thecomposition and the physical properties of these catalysts are given inTable 3.

50 cc of the regenerated catalyst 1 was filled in the former stage of asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc), and 50cc of the fresh catalyst 1 in the latter stage thereof. Through thereactor, first passed was light-gravity gas oil (its sulfur content wascontrolled to be 2.5% by adding thereto a sulfurizing agent, DMDS), at aflow rate of 135 kg/cm³ of hydrogen at 250° C. for 24 hours forpre-sulfurization. Next, the normal-pressure residual oil mentionedabove was passed through it for hydro-denitrification. The reactionconditions are given in Table 6; and the properties of the processed oilare in Table 7.

Example 2 (first aspect of the invention)

The same process as in [Example 1] was repeated, except that 25 cc ofthe regenerated catalyst 1 was filled in the former stage of asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc), and 75cc of the fresh catalyst 1 in the latter stage thereof. The propertiesof the processed oil are given in Table 7.

Example 3 (first aspect of the invention)

In the same manner as in [Example 1], washed catalyst 2 and regeneratedcatalyst 2 were prepared from a commercially-available catalyst carryingnickel and molybdenum on an alumina-phosphorus carrier (this is referredto as fresh catalyst 2). The composition and the physical properties ofthese catalysts are given in Table 4. Next, the same process as in[Example 1] was repeated, except that 50 cc of the regenerated catalyst2 was filled in the former stage of a small-sized, high-pressurefixed-bed reactor (capacity: 200 cc), and 50 cc of the fresh catalyst 2in the latter stage thereof. The properties of the processed oil aregiven in Table 7.

Example 4 (first aspect of the invention)

Like in [Example 1], the fresh catalyst 1 was filled in areduced-pressure light oil hydro-desulfurization device, into which wasapplied reduced-pressure light oil from the Middle East, for 8000 hours.Hydro-desulfurizing the light oil was continued while the reactiontemperature was so monitored that the sulfur content of the essentialfraction (distillate having a boiling point of not lower than 360° C.)of the processed oil could be stabilized on a constant level. This is toprepare a used catalyst from the fresh catalyst. The properties of thereduced-pressure light oil processed herein are given in Table 1; andthe reaction conditions for desulfurization are in Table 2. From theused catalyst, prepared were washed catalyst 3 and regenerated catalyst3 in the same manner as in [Example 1]. The composition and the physicalproperties of these catalysts are given in Table 5. Next, the sameprocess as in [Example 1] was repeated, except that 50 cc of theregenerated catalyst 3 was filled in the former stage of a small-sized,high-pressure fixed-bed reactor (capacity: 200 cc), and 50 cc of thefresh catalyst 1 in the latter stage thereof. The properties of theprocessed oil are given in Table 7.

Example 5 (second aspect of the invention)

50 cc of the fresh catalyst 1 was filled in the former stage of asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc), and 50cc of the regenerated catalyst 1 in the latter stage thereof. Throughthe reactor, first passed was light-gravity gas oil (its sulfur contentwas controlled to be 2.5% by adding thereto a sulfurizing agent, DMDS),at a flow rate of 135 kg/cm³ of hydrogen at 250° C. for 24 hours forpre-sulfurization. Next, the normal-pressure residual oil mentionedabove was passed through it for desulfurization. The reaction conditionsare given in Table 6; and the properties of the processed oil are inTable 7.

Example 6 (second aspect of the invention)

The same process as in [Example 5] was repeated, except that 75 cc ofthe fresh catalyst 1 was filled in the former stage of a small-sized,high-pressure fixed-bed reactor (capacity: 200 cc), and 25 cc of theregenerated catalyst 1 in the latter stage thereof. The properties ofthe processed oil are given in Table 7.

Example 7 (second aspect of the invention)

The same process as in [Example 5] was repeated, except that 50 cc ofthe fresh catalyst 2 was filled in the former stage of a small-sized,high-pressure fixed-bed reactor (capacity: 200 cc), and 50 cc of theregenerated catalyst 2 in the latter stage thereof. The properties ofthe processed oil are given in Table 7.

Example 8 (second aspect of the invention)

The same process as in [Example 5] was repeated, except that 50 cc ofthe fresh catalyst 1 was filled in the former stage of a small-sized,high-pressure fixed-bed reactor (capacity: 200 cc), and 50 cc of theregenerated catalyst 3 in the latter stage thereof. The properties ofthe processed oil are given in Table 7.

Example 9 (third aspect of the invention)

A small-sized, high-pressure fixed-bed reactor (capacity: 200 cc) wasfilled with 25 cc of the fresh catalyst 1, then 25 cc of the regeneratedcatalyst 1, then 25 cc of the fresh catalyst 1, and finally 25 cc of theregenerated catalyst 1 in that order from the upstream side of oil flow.Through the reactor, first passed was light-gravity gas oil (its sulfurcontent was controlled to be 2.5% by adding thereto a sulfurizing agent,DMDS), at a flow rate of 135 kg/cm³ of hydrogen at 250° C. for 24 hoursfor pre-sulfurization. Next, the normal-pressure residual oil mentionedabove was passed through it for hydrogenation. The reaction conditionsare given in Table 6; and the properties of the processed oil are inTable 7.

Example 10 (third aspect of the invention)

The same process as in [Example 9] was repeated, except that asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc) wasfilled with 45 cc of the fresh catalyst 1, then 25 cc of the regeneratedcatalyst 1, and finally 30 cc of the fresh catalyst 1 in that order fromthe upstream side of oil flow. The properties of the processed oil aregiven in Table 7.

Example 11 (third aspect of the invention)

The same process as in [Example 9] was repeated, except that asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc) wasfilled with 10 cc of the fresh catalyst 2, then 25 cc of the regeneratedcatalyst 2, then 30 cc of the fresh catalyst 2, then 25 cc of theregenerated catalyst 2, and finally 10 cc of the fresh catalyst 2 inthat order from the upstream side of oil flow. The properties of theprocessed oil are given in Table 7.

Example 12 (third aspect of the invention)

The same process as in [Example 9] was repeated, except that asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc) wasfilled with 30 cc of the fresh catalyst 1, then 50 cc of the regeneratedcatalyst 3, and finally 20 cc of the fresh catalyst 1 in that order fromthe upstream side of oil flow. The properties of the processed oil aregiven in Table 7.

Example 13 (third aspect of the invention)

The same process as in [Example 1] was repeated, except that asmall-sized, high-pressure fixed-bed reactor (capacity: 200 cc) wasfilled with a mixed catalyst that had been prepared by uniformly mixing50 cc of the fresh catalyst 1 and 50 cc of the regenerated catalyst 1.The properties of the processed oil are given in Table 7.

TABLE 1 Normal- Reduced- Pressure Pressure Method for Items MeasuredResidual Oil Light Oil Measurement Density (15° C., g/cm³) 0.962 0.916JIS K-2249 Kinematic Viscosity (50° C., 290 61 JIS K-2283 cSt)Carbonaceous Residue 9.33 0.23 JIS K-2270 (wt. %) Asphaltene (wt. %)2.98 — IP 143 Impurity Content (by weight) Sulfur Content (%) 3.48 2.42JIS K-2541 Nitrogen Content (ppm) 1840 1010 JIS K-2609 Vanadium Content(ppm) 37.6 0.2 JPI-5S-10-79 Nickel Content (ppm) 10.8 — JPI-5S-11-79Distillate Fractions JIS K-2254 (% by volume) up to 340° C. 6.2 6.3 from340 to 525° C. 46.2 86.2 over 525° C. 47.6 7.5

TABLE 2 Example 1 Example 4 normal-pressure reduced-pressure StartingOil residual oil light oil Hydrogen Partial Pressure (kg/cm²) 130 60Liquid Hourly Space Velocity (/hr) 0.3 1.8 Ratio of Hydrogen/Oil(Nm³/kl) 850 500 Sulfur Content of Essential 0.3 0.25 Fraction ofProcessed Oil (wt. %) Reaction Time Continued (hr) 8000 8000

TABLE 3 Fresh Washed Regenerated Type of Catalyst Catalyst 1 Catalyst 1Catalyst 1 Carrier alumina alumina alumina Metal Content (wt. %)molybdenum 8.8 8.2 8.3 nickel 2.4 3.2 3.2 vanadium — 7.4 7.4 CarbonContent (wt. %) — 28.3 0.8 Pore Structure Specific Surface Area (m²/g)197 96 167 Pore Volume (cc/g) 0.6 0.25 0.52

TABLE 4 Fresh Washed Regenerated Type of Catalyst Catalyst 2 Catalyst 2Catalyst 2 Carrier alumina/ alumina/ alumina/ phosphorus phosphorusphosphorus (1.7%) (1.6%) (1.6%) Metal Content (wt. %) molybdenum 8.8 8.08.1 nickel 2.3 3.9 3.9 vanadium — 15.1 15.1 Carbon Content (wt. %) —23.3 0.6 Pore Structure Specific Surface Area (m²/g) 183 88 145 PoreVolume (cc/g) 0.6 0.25 0.52

TABLE 5 Fresh Washed Regenerated Type of Catalyst Catalyst 3 Catalyst 3Catalyst 3 Carrier alumina alumina alumina Metal Content (wt. %)molybdenum 8.8 8.8 8.8 nickel 2.4 2.3 2.3 vanadium 0.6 0.6 CarbonContent (wt. %) 16.6 0.2 Pore Structure Specific Surface Area (m²/g) 197122 184 Pore Volume (cc/g) 0.6 0.34 0.52

TABLE 6 Starting Oil Normal-Pressure Residual Oil Reaction Temperature(° C.) 370 Hydrogen Partial Pressure (kg/cm²) 135 Liquid Hourly SpaceVelocity (/hr) 0.3 Ratio of Hydrogen/Oil (Nm³/kl) 850 Reaction TimeContinued (hr) 500

TABLE 7 Metal Content Nitrogen Content Sulfur Content (V + Ni) (ppm byweight) (% by weight) (ppm by weight) Starting Oil 1840  3.48 48(normal-pressure residual oil) Example 1 720 0.46 16 Example 2 680 0.3212 Example 3 640 0.41 19 Example 4 650 0.29 8 Example 5 810 0.34 11Example 6 770 0.26 8 Example 7 740 0.30 15 Example 8 660 0.28 8 Example9 700 0.32 10 Example 10 670 0.24 8 Example 11 620 0.29 13 Example 12650 0.27 8 Example 13 690 0.30 9

INDUSTRIAL APPLICABILITY

As described in detail hereinabove, in the method of heavy oilhydrogenation of the invention for which the catalyst disposition isspecifically defined, heavy oil can be well hydrogenated under the sameconditions as those for ordinary heavy oil hydrogenation with freshcatalysts. The method is significantly effective for efficientutilization of used catalysts.

What is claimed is:
 1. A method of hydro-denitrifying heavy oil in areaction zone filled with a catalyst, which is characterized by catalystdisposition of such that a regenerated catalyst is disposed in theformer stage of at least a part of the reaction zone and a freshcatalyst is disposed in the latter stage thereof, (i) the regeneratedcatalyst being obtained by first washing and then oxidizing a usedcatalyst and (ii) the regenerated catalyst and the fresh catalyst beingcarried on an oxide carrier of alumina containing at least one oxide ofphosphorus, boron or silicon.
 2. The hydro-denitrifying method asclaimed in claim 1, wherein the amount of the fresh catalyst filled inat least a part of the reaction zone falls between 20 and 95% by volumeand that of the regenerated catalyst filled therein falls between 5 and80% by volume.
 3. A method of hydro-desulfurizing heavy oil in areaction zone filled with a catalyst, which is characterized by catalystdisposition of such that a fresh catalyst is disposed in the formerstage of at least a part of the reaction zone and a regenerated catalystis disposed in the latter stage thereof, (i) the regenerated catalystbeing obtained by first washing and then oxidizing a used catalyst and(ii) the regenerated catalyst and the fresh catalyst being carried on anoxide carrier of alumina containing at least one oxide of phosphorus,boron or silicon.
 4. The hydro-desulfurizing method as claimed in claim3, wherein the amount of the regenerated catalyst filled in at least apart of the reaction zone falls between 5 and 80% by volume and that ofthe fresh catalyst filled therein falls between 20 and 95% by volume. 5.A method of hydrogenating heavy oil, for which is used a reaction zonecomprising at least three reaction layers of regenerated catalyst layersand fresh catalyst layers disposed alternately, (i) the regeneratedcatalyst being obtained by first washing and then oxidizing a usedcatalyst and (ii) the regenerated catalyst and the fresh catalyst beingcarried on an oxide carrier of alumina containing at least one oxide ofphosphorus, boron or silicon.
 6. The method of hydrogenating heavy oilas claimed in claim 5, wherein the liquid hourly space velocity (LHSV)of the heavy oil passing through the regenerated catalyst layer to behydrogenated therethrough is larger than 1 hr⁻¹.
 7. A method ofhydrogenating heavy oil, for which is used a reaction zone comprising aregenerated catalyst and a fresh catalyst and having at least a mixedlayer of the two, (i) the regenerated catalyst being obtained by firstwashing and then oxidizing a used catalyst and (ii) the regeneratedcatalyst and the fresh catalyst being carried on an oxide carrier ofalumina containing at least one oxide of phosphorus, boron or silicon.8. The method of hydrogenating heavy oil as claimed in claim 5, whereinthe amount of the regenerated catalyst filled in the reaction zone fallsbetween 5 and 80% by volume and that of the fresh catalyst filledtherein falls between 20 and 95% by volume.
 9. The method ofhydrogenating heavy oil as claimed in claim 5, wherein the vanadiumcontent of the regenerated catalyst is at most 35% by weight.
 10. Themethod of hydrogenating heavy oil as claimed in claim 5, wherein thecarbon content of the regenerated catalyst is at most 15% by weight. 11.The method of hydrogenating heavy oil as claimed in claim 5, wherein thespecific surface area of the regenerated catalyst falls between 60 and200 m²/g.
 12. The method of hydrogenating heavy oil as claimed in claim5, wherein the pore volume of the regenerated catalyst falls between 0.3and 1.0 cc/g.
 13. The method of hydrogenating heavy oil as claimed inclaim 5, wherein the regenerated catalyst is from a used catalyst havingat least one metal of molybdenum, tungsten, cobalt and nickel carried onsaid oxide carrier, the catalyst having been used for hydrogenatingmineral oil and then regenerated.
 14. The method of hydrogenating heavyoil as claimed in claim 13, wherein the metal carried on said oxidecarrier is nickel and molybdenum.
 15. The method of hydrogenating heavyoil as claimed in claim 13, wherein the metal carried on said oxidecarrier is nickel or cobalt, and molybdenum.
 16. The method ofhydrogenating heavy oil as claimed in claim 13, wherein the nickel orcobalt content of the catalyst having the metal carried on its carrierfalls between 0.1 and 10% by weight and the molybdenum content thereoffalls between 0.1 and 25% by weight.
 17. The method of hydrogenatingheavy oil as claimed in claim 9, which is for hydro-denitrifying heavyoil.
 18. The method of hydrogenating heavy oil as claimed in claim 9,which is for hydro-desulfurizing heavy oil.
 19. The method ofhydrogenating heavy oil as claimed in claim 7, wherein the vanadiumcontent of the regenerated catalyst is at most 35% by weight.
 20. Themethod of hydrogenating heavy oil as claimed in claim 7, wherein thecarbon content of the regenerated catalyst is at most 15% by weight. 21.The method of hydrogenating heavy oil as claimed in claim 7, wherein thespecific surface area of the regenerated catalyst falls between 60 and200 m²/g.
 22. The method of hydrogenating heavy oil as claimed in claim7, wherein the pore volume of the regenerated catalyst falls between 0.3and 1.0 cc/g.
 23. The method of hydrogenating heavy oil as claimed inclaim 7, wherein the regenerated catalyst is from a used catalyst havingat least one metal of molybdenum, tungsten, cobalt and nickel carried onsaid oxide carrier, the catalyst having been used for hydrogenatingmineral oil and then regenerated.
 24. The method of hydrogenating heavyoil as claimed in claim 23, wherein the metal carried on said oxidecarrier is nickel and molybdenum.
 25. The method of hydrogenating heavyoil as claimed in claim 23, wherein the metal carried on said oxidecarrier is nickel or cobalt, and molybdenum.
 26. The method ofhydrogenating heavy oil as claimed in claim 23, wherein the nickel orcobalt content of the catalyst having the metal carried on its carrierfalls between 0.1 and 10% by weight and the molybdenum content thereoffalls between 0.1 and 25% by weight.
 27. The method of hydrogenatingheavy oil as claimed in claim 19, which is for hydro-denitrifying heavyoil.
 28. The method of hydrogenating heavy oil as claimed in claim 19,which is for hydro-desulfurizing heavy oil.